slang for "backside," first attested 1860 in nautical slang, in popular use from 1930; from Amer.Eng. pronunciation of
arse (q.v.). The loss of
-r- before
-s- attested in several other words (e.g.
burst/bust, curse/cuss, horse/hoss, barse/bass). Indirect evidence of the change from
arse to
ass can be traced to 1785 (in euphemistic avoidance of
ass "donkey" by polite speakers) and perhaps to Shakespeare, if Nick
Bottom transformed into a donkey in "A Midsummer Night's Dream" (1594) is the word-play some think it is. Meaning "woman regarded as a sexual object" is from 1942.
Asshole first attested 1935.